Current camera systems typically include an illuminating system for low light situations. The illuminator consists of a flash tube and reflector that are designed to illuminate the scene area captured by the camera on film. In these systems, a capacitor is charged from a battery to store a specific amount of energy. When the shutter of the camera is opened, the capacitor discharges through the flash tube to create a burst of light. It is desirable to limit the size of the camera, so the typical flash system has a maximum range of up to about 16 feet. Larger flash units exist that allow for illumination at greater distances and are typically provided as separate, large units.
One photographic technique that provides for improved image quality is the use of a reflecting surface to diffuse the flash and illuminate the subject off-axis from the light gathering (optical) axis of the camera. The simplest means for doing this is to use a white, reflective ceiling, and to direct the flash output in a bouncing configuration against the ceiling and then onto the subject to be photographed. This effect improves the image quality only when an appropriate reflecting surface is present and when the subject to be photographed is far enough away from the camera to prevent harsh facial shadows, but not so far away that the flash capacity cannot adequately illuminate the scene. In a bounce mode, the effective flash range is reduced by two stops, so bounce flash for a 12 foot flash range may be reduced to 8 feet or less. In addition, harsh shadows occur when the subject is closer than about 3 feet.
As a result, in a typical flash system, bounce flash will improve images when a ceiling is present and the subject to be photographed is between about 3 and 8 feet from the camera. This type of situation represents a significant portion of flash pictures. If the operator is aware of these operating parameters, a significant majority of captured indoor images can be accomplished with a bounce flash, resulting in improved image quality.
In U.S. Pat. No. 4,384,238, an illumination technique is disclosed in which two flashtubes 12 and 15, sharing a common capacitor, are built into a camera. Preferably flashtube 12, the bounce flashtube, is fired first. When a photosensor 18 senses that a predetermined fraction of a desired total amount of light has been reflected from the scene, flashtube 12 is quenched and the remaining energy in the capacitor is directed into flashtube 15 to directly illuminate the scene. If the camera is operated outdoors or in a room with a low-optically reflective ceiling, or if the distance between the camera and the subject is large, flashtube 12 is still fired (Col. 4, lines 26-39).
In U.S. Pat. No. 5,136,312, discloses a flash system wherein a source of flash illumination operates selectively in a first mode for projecting light in a first direction toward an indirect reflecting surface to illuminate a subject indirectly and in a second mode for projecting light in a second direction to illuminate a subject directly. Electromagnetic radiation reflected directly from the indirect reflecting surface is sensed directly to provide a signal containing information about the indirect reflecting surface. This information is used to control the selective projection of light in the first and second directions to control the quantities of indirect and direct light which illuminate the subject.